1. Field of the Invention
The present invention relates generally to primer assemblies and, more particularly, to an improved bayonet type primer assembly for medium caliber ammunition.
2. Discussion of the Prior Art
Bayonet type primer assemblies have been used for many years in ignition systems of medium caliber ammunition, such as ammunition that is fired from a fighting vehicle. For example, tank ammunition comprises a 120 mm cartridge that includes a primer assembly threaded into the base of a cartridge case. The primer assembly is embedded into a propelling charge that is contained within the cartridge case in proximity to a projectile.
The primer assembly typically includes a primer head and a tubular body portion having an open end, a closed end, an interior chamber and flash holes in a wall of the body. A pyrotechnic formulation such as a nitrocellulose and black powder formulation in a strand form (e.g., benite) is disposed within the chamber. The primer head is mounted externally to the tubular body to close the open end of the tubular body. The primer head assembly includes an ignition element that is located in proximity with the pyrotechnic formation when the primer head is mounted to the tubular body. When activated, the ignition element ignites the pyrotechnic formulation. Ignition flame from the pyrotechnic formulation passes through the flash holes and ignites the propellant charge within the cartridge case to propel the projectile out of the casing and a barrel of the vehicle. Two piece primer assemblies of this type are disclosed in commonly assigned U.S. Pat. No. 5,465,665, entitled “Primer”, by Steven F. Diehl, issued Nov. 14, 1995, and U.S. Pat. No. 5,052,302, entitled “Unpressurized Combustible Primer For Cannon Cartridges”, by Ralph M. Taddeo et al., issued Oct. 1, 1991. The disclosures of these U.S. patents are incorporated by reference herein in their entireties.
Most conventional primer assemblies include metallic components. During the ignition process the metallic components become extremely hot, for example, the surface temperature of the components exceeds the ignition temperatures of combustible components of the 120 mm ammunition. After ignition, the cartridge case including the primer assembly is ejected into the confines of the fighting vehicle. The ejected hot metallic components present a serious potential hazard to personnel within the fighting vehicle. For example, the ejected hot metallic components may contact an ammunition round that was being held ready for loading, or the ejected components may land on a next round stored in the vehicle and start a fire within the close confines of the fighting vehicle.
The aforementioned U.S. patents describe solutions to the problem presented by the ejected hot metallic components within the confines of the fighting vehicle.
The inventor has realized that further improvements over the conventional arrangements may be achieved by employing an improved primer assembly having a tubular body that accepts a primer head and ignition element within an internal diameter. For example, the inventor has realized that conventional primer assembly configurations having the primer head mount externally on a tubular body have drawbacks both during assembly and in use. For example, external mounting of the primer head makes assembly unduly cumbersome as particular care is required to ensure that ignition components are properly aligned within the internal chamber of the tubular body. Additionally, the externally mounted primer head may become detached from the tubular body due to vibration from movement of the fighting vehicle or under the extreme temperature and pressure ignition conditions. The separation of the primer assembly components may result in damage to the barrel of the fighting vehicle upon firing and/or complicate loading of a next round as the separate, extremely hot components must be individually removed from the barrel. The inventor has realized that by incorporating the primer body, primer head and ignition element into a one-piece construction increases the capacity of the primer assembly to dissipate heat more efficiently and quicker. Accordingly, the inventor has realized that it is desirable for primer assemblies to have a tubular body that accepts a primer head and ignition element within an internal diameter.